Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/07 attributes/attributesdemo/module1.vb

Text File | 2002-03-16 | 7KB | 190 lines

Imports System.Runtime.InteropServices

Module MainModule

    Sub Main()
        ' Run one of the Textxxxx procedures below by uncommenting only one statement

        'TestFieldOffset()
        'TestUnions()
        'TestDllImport()
        'TestConditionalAttribute()
        'TestObsoleteAttribute()
        'TestListVersioningAttributes()

        ' These statements are usuful when running inside Visual Studio.NET
        Console.WriteLine("")
        Console.WriteLine(">>> write Enter to terminate the program <<<")
        Console.ReadLine()
    End Sub

    ' This procedure tests the FieldOffset attributes
    Sub TestFieldOffset()
        ' Split a color into its components.
        Dim rgb As ARGBColor
        rgb.Value = &H112233         ' This is equal to 1122867.
        Console.WriteLine(String.Format("Red={0}, Green={1}, Blue={2}", _
            rgb.Red, rgb.Green, rgb.Blue))
        ' => Red=51, Green=34, Blue=17
    End Sub

    ' this procedure tests "unions"

    Sub TestUnions()
        Dim it As IntegerTypes

        it.Short0 = 517                  ' hex 0205
        Console.WriteLine(it.Byte0)        ' => 5
        Console.WriteLine(it.Byte1)        ' => 2

        Console.WriteLine(it.LowByte(517))           ' => 5
        Console.WriteLine(it.HighByte(517))          ' => 2
        Console.WriteLine(it.LowWord(&HFFFF1000))    ' => 4096
        Console.WriteLine(it.HighWord(&HFFFF1000))   ' => -1
    End Sub

    ' Note that this code works even though the actual procedure
    ' is named FindWindowA, because the compiler tracks it automatically.
    <DllImport("user32")> _
    Function FindWindow _
        (ByVal lpClassName As String, ByVal lpWindowName As String) As Integer
        ' no implementation code
    End Function

    <DllImport("user32")> _
    Function MoveWindow _
        (ByVal hWnd As Integer, ByVal x As Integer, ByVal y As Integer, _
        ByVal nWidth As Integer, ByVal nHeight As Integer, _
        ByVal bRepaint As Integer) As Integer
        ' no implementation code
    End Function

    ' this procedure tests the DllImport attribute

    Sub TestDllImport()
        ' NOTE: launch Notepad on an empty document before running this code.
        Dim hWnd As Integer = FindWindow(Nothing, "Untitled - Notepad")
        ' If found, resize it and move it to upper-left corner.
        If hWnd <> 0 Then MoveWindow(hWnd, 0, 0, 600, 300, 1)
    End Sub

    ' this procedure tests the Conditional attribute

    Sub TestConditionalAttribute()
        LogMsg("Program is starting")
        ' ..
        LogMsg("Program is ending")
    End Sub

    ' Goto to the Configuration Properties | Build to set the LOG constant
    ' to a non-zero value to include this procedure

    <Conditional("LOG")> _
    Sub LogMsg(ByRef MsgText As String)
        Console.WriteLine(MsgText)
    End Sub

    ' this procedure tests the Obsolete attribute

    Sub TestObsoleteAttribute()
        Dim arr() As String
        ' next line is flagged as a warning
        BubbleSort(arr)

        ' *** uncomment next line to see a compile error
        ' BubbleSort2(arr)
    End Sub

    ' Mark the BubbleSort as obsolete - this causes a compiler warning
    <Obsolete("Replace BubbleSort with ShellSort")> _
    Sub BubbleSort(ByVal arr() As String)
        ' ...
    End Sub

    ' Mark the BubbleSort2 as obsolete - this causes a compiler error
    <Obsolete("Replace BubbleSort with ShellSort", True)> _
    Sub BubbleSort2(ByVal arr() As String)
        ' ...
    End Sub

    ' this procedure lists the Versioning attribute
    Sub TestListVersioningAttributes()
        Dim attributes() As Object
        Dim att As VersioningAttribute
        Dim method As System.Reflection.MethodInfo
        Dim attType As Type = GetType(VersioningAttribute)
        Dim classType As Type = GetType(TestClass)

#Const ASSUME_MULTIPLE_OCCURRENCES = True

#If ASSUME_MULTIPLE_OCCURRENCES Then
        ' this version shows how to query for custom attributes that
        ' can have multiple occurrences

        ' Retrieve all the custom attributes of type VersioningAttribute.
        attributes = Attribute.GetCustomAttributes(classType, attType)

        ' Check whether the array contains any element (it should contain one).
        If attributes.Length > 0 Then
            ' Move to a specific type variable so we can use early binding.
            att = DirectCast(attributes(0), VersioningAttribute)
            ' Display versioning information on the TestClass itself.
            Console.WriteLine("Class TestClass")
            Console.WriteLine("  Author = " & att.Author)
            Console.WriteLine("  Version = " & att.Version.ToString)
            Console.WriteLine("  Tested = " & att.Tested.ToString)
        End If

        ' Iterate over all the methods in TestClass.
        For Each method In classType.GetMethods
            ' Get Versioning attributes for this method.
            attributes = Attribute.GetCustomAttributes(method, attType)
            ' If there are custom Versioning attributes.
            If attributes.Length > 0 Then
                ' Display the name of this method.
                Console.WriteLine("Method " & method.Name)
                ' Get a Versioning object to use early binding.
                att = DirectCast(attributes(0), VersioningAttribute)
                ' Display versioning information on this method.
                Console.WriteLine("  Author = " & att.Author)
                Console.WriteLine("  Version = " & att.Version.ToString)
                Console.WriteLine("  Tested = " & att.Tested.ToString)
            End If
        Next
#Else

        ' this simpler version assumes that the attribute has no
        ' multiple occurrences.

        ' Retrieve the (only) VersioningAttribute, or Nothing.
        att = DirectCast(Attribute.GetCustomAttribute(classType, attType), VersioningAttribute)

        ' Check whether the attribute was found.
        If Not (att Is Nothing) Then
            ' Display versioning information on the TestClass itself.
            Console.WriteLine("Class TestClass")
            Console.WriteLine("  Author = " & att.Author)
            Console.WriteLine("  Version = " & att.Version.ToString)
            Console.WriteLine("  Tested = " & att.Tested.ToString)
        End If

        ' Iterate over all the methods in TestClass.
        For Each method In classType.GetMethods
            ' Get the Versioning attribute for this method.
            att = DirectCast(Attribute.GetCustomAttribute(method, attType), VersioningAttribute)
            ' If there are custom Versioning attributes.
            If Not (att Is Nothing) Then
                ' Display the name of this method.
                Console.WriteLine("Method " & method.Name)
                ' Display versioning information on this method.
                Console.WriteLine("  Author = " & att.Author)
                Console.WriteLine("  Version = " & att.Version.ToString)
                Console.WriteLine("  Tested = " & att.Tested.ToString)
            End If
        Next
#End If

    End Sub

End Module